PubMed Health⌕ Search

Biomedical subjects

C G Shaw

Publications and source records attributed to C G Shaw.

At least 19 recordsLinked to original sources
PubMed2003

Prediction of cervical spine injury risk for the 6-year-old child in frontal crashes.

This article presents a series of 49 km/h sled tests using the Hybrid III 6-year-old dummy in a high-back booster, a low-back booster, and a three-point belt. Although a 10-year review at a level I trauma center showed that noncontact cervical spine injuries are rare in correctly restrained booster-age children, dummy neck loads exceeded published injury thresholds in all tests. The dummy underwent extreme neck flexion during the test, causing full-face contact with the dummy's chest. These dummy kinematics were compared to the kinematics of a 12-year-old cadaver tested in a similar impact environment. The cadaver test showed neck flexion, but also significant thoracic spinal flexion which was nonexistent in the dummy. This comparison was expanded using MADYMO simulations in which the thoracic spinal stiffness of the dummy model was decreased to give a more biofidelic kinematic response. We conclude that the stiff thoracic spine of the dummy results in high neck forces and moments that are not representative of the true injury potential.

Accidents, Traffic↗
PubMed2002

Prediction of cervical spine injury risk for the 6-year-old child in frontal crashes.

This paper presents a series of 49 km/h sled tests using the Hybrid III 6-year-old dummy in a high-back booster, a low-back booster, and a three-point belt. Although it is shown that non-contact cervical spine injuries are rare in correctly restrained children in this age group, neck loads exceeded published injury thresholds in all tests. The dummy kinematics were compared to the kinematics of a 12-year-old cadaver tested in a similar impact environment. This comparison was expanded using MADYMO simulations. It is concluded that the stiff thoracic spine of the dummy results in high neck forces and moments that are not representative of the true injury potential.

Accidents, Traffic↗
PubMed1998

Retention of supportive properties by eggcrate and foam wheelchair cushions.

This study investigated the reported lack of ability of the eggcrate cushion (EC) to provide wheelchair users with adequate support necessary for comfort and tolerably low-peak sitting pressures over time. The primary parameter used to quantify the ability of the cushion to distribute load was the indention force deflection (IFD) metric. The EC was compared to a high-density planar foam cushion (HD). The IFD was measured for both cushions after successive periods of compression to simulate use. Study results failed to support the common perception that the soft EC would lose its supportive properties more rapidly than the much firmer HD cushion. Although the initial IFD of the EC was much lower than that of the HD, a smaller percentage of its IFD was lost after compression. This difference between the two cushions likely was due to differences in packaging. The EC was rolled into a cylinder, compressing it to 60% of its original thickness; the HD was packaged without compression.

Compressive Strength↗
PubMed1993

Seat cushion comparison for nursing home wheelchair users.

Finding solutions to the seating problems of nursing home wheelchair users is challenging due to the lack of data regarding the pressure-relieving and comfort performance of wheelchair cushions for this population. This study's goal was to determine whether commercially available seat cushions provide better pressure relief and comfort than do traditionally provided or "makeshift" cushions or pads. Using a repeated measures design, 21 nursing home wheelchair users were enlisted to help evaluate two traditionally provided or "makeshift" cushions or pads and two selected commercially available seat cushions. The peak sitting pressures for 20 subjects were recorded using an Oxford pressure monitor. Twenty-one subjects were asked to score the test cushions' comfort. Due to the somewhat surprising results for the traditionally provided eggcrate cushion, the results fell short of supporting our initial hypothesis. Nevertheless, the study did identify three cushions, the eggcrate, the gel/foam, and the foam, which provided significantly lower peak sitting pressure averages than those recorded for the mix of cushions and pads used by 50 residents in a previous survey. Select commercially available seat cushions can offer nursing home residents lower sitting pressures and increased comfort. Further investigation is required to assess the long-term performance of these and other seat cushions and to explore the predictive benefits of the statistically significant relationship identified between peak sitting pressure and comfort.

Aged↗
PubMed1986

Pulsed-injection method for blood flow velocity measurement in intraarterial digital subtraction angiography.

The pulsed-injection method for measuring the velocity of blood flow in intraarterial digital subtraction angiography is described. With this technique, contrast material is injected at a pulsing frequency as high as 15 Hz, so that two or more boluses can be imaged simultaneously. The velocity of flow is determined by measuring the spacing between the boluses and multiplying it by the pulsing frequency. Results of tests with phantoms correlate well with flow measurements obtained with a graduated cylinder for velocities ranging from 8 to 60 cm/sec. The potential of the method for time-dependent velocity measurement has been demonstrated with simulated pulsatile flows.

Angiography↗
PubMed1985

Quantitative digital subtraction angiography: two scanning techniques for correction of scattered radiation and veiling glare. Work in progress.

Scattered radiation and veiling glare in digital subtraction angiography degrade contrast signals in a nonlinear and nonuniform way. This effect prohibits direct use of image data for accurate iodine measurement or energy subtraction imaging. Two techniques based on the use of scanning lead bars were proposed to measure the spatial distribution of scattered radiation and veiling glare in the unprocessed image data. With either technique, signals behind the lead bars were used to estimate the scatter-glare component and remove it from the image data. The scanning-lead-bar techniques can be used to reduce the scatter-glare component by a factor of up to 10. The scatter-glare correction leads to the recovery of degraded contrast signals and achieves reasonable linearity, uniformity, and consistency in the contrast measurement.

Angiography↗
PubMed1982

A technique of scatter and glare correction for videodensitometric studies in digital subtraction videoangiography.

The logarithmic amplification of video signals and the availability of data in digital form make digital subtraction videoangiography a suitable tool for videodensitometric estimation of physiological quantities. A system for this purpose was implemented with a digital video image processor. However, it was found that the radiation scattering and veiling glare present in the image-intensified video must be removed to make meaningful quantitations. An algorithm to make such a correction was developed and is presented. With this correction, the videodensitometry system was calibrated with phantoms and used to measure the left ventricular ejection fraction of a canine heart.

Absorptiometry, Photon↗
PubMed1982

Computerized fluoroscopy: new technique for the noninvasive evaluation of the aorta, coronary artery bypass grafts, and left ventricular function.

A computerized fluoroscopy system has been developed on the basis of real-time digital processing of x-ray transmission data from traditional image-intensified fluoroscopy equipment. High-quality visualization of any part of the arterial system is obtained following intravenous injection of 0.5 to 0.75 ml/kg of iodinated contrast materials. This report describes the use of this technique to evaluate the aortic arch, left ventricular function, and coronary artery bypass graft patency. Fifty intravenous studies were performed in 25 patients. Among 20 patients with coronary artery bypass grafts, computerized fluoroscopy correctly identified 11 of 15 patent grafts and 11 of 11 occluded grafts as confirmed by standard coronary arteriography in 11 of these patients. Unlike computerized tomography, our technique gives a longitudinal view of the bypass graft much like direct coronary angiography. Aortic arch studies included demonstration of a right aortic arch with a small left subclavian artery, a coarctation, and a normal aortic arch in a trauma patient with a wide mediastinum. Segmental wall motion abnormalities were clearly identified by a modification of the technique which produces a negative outline on the ventriculogram in dyskinetic segments. Ejection fractions may be calculated by determining the amount of iodine in the ventricle in systole and diastole. This technique may also be used to evaluate carotid disease and peripheral vascular disease in patients undergoing coronary artery bypass procedures. Computerized fluoroscopy, therefore, allows evaluation of the entire cardiovascular system by the relatively noninvasive technique of intravenous angiography.

Angiography↗
PubMed1981

Digital video subtraction angiography for evaluation of peripheral vascular disease.

Digital video subtraction angiography (DVSA) has been employed to study a variety of peripheral vascular problems, using equipment developed at the University of Wisconsin. The technique is relatively simple and safe and has good patient acceptance. Experience indicates that in selected patients it is a satisfactory alternative to standard arteriography for screening and for definitive evaluation and on occasion may yield information not obtainable with conventional methods. It can aid in the performance of transluminal angioplasty and is suitable for serial evaluation of atherosclerotic vessels and bypass grafts.

Adult↗
PubMed1980

Clinical applications of computerized fluoroscopy: the extracranial carotid arteries.

Preliminary results obtained with a new computerized fluoroscopic apparatus in examination of the extracranial carotid arteries are described. All patients had clinical signs of symptoms of extracranial occlusive vascular disease. In most cases, image quality was sufficient to display patency of the internal carotid arteries, with excellent correlation between intravenous and conventional angiography. While the new technique is not totally noninvasive, it does eliminate many of the risks and costs of conventional arteriography.

Arterial Occlusive Diseases↗
PubMed1980

Computerized fluoroscopy: digital subtraction for intravenous angiocardiography and arteriography.

Computerized fluoroscopy is a system comprising on-line digital time and energy subtraction algorithms designed to isolate and enhance the iodine signal from image intensified fluoroscopy. The apparatus is described and its use for time subtraction intravenous arteriography of the carotid, abdominal, extremely arteries, as well as the heart, is illustrated. Vascular diseases such as stenoses, obstruction, emboli, ulcerative plaques, and aneurysms are readily demonstrated. The technique has a potential for evaluating cardiac motion and the patency of coronary artery bypass grafts. The method appears to be a safe and less expensive alternative to catheter arteriography and angiocardiography in certain instances.

Adult↗
PubMed1979

A hybrid computerized fluoroscopy technique for noninvasive cardiovascular imaging.

The excellent linearity of digital image storage and retrieval permits hybrid analog-digital subtraction to extend the spatial resolution of two previously developed algorithms which employed entirely digital apparatus. A low resolution, time-integrated preinjection digital mask image is reconverted to analog form and subtracted from live analog video images of iodine administered by peripheral intravenous injection to produce a high resolution display of the cardiovascular system with contrast ten times greater than conventional fluoroscopy. Preliminary studies in dogs are compared with images obtained with our digital subtraction algorithms.

Animals↗
PubMed1977

Analysis of water soluble vitamins by high pressure liquid chromatography.

Resolution of the water-soluble vitamins--pyridoxin, riboflavin, niacinamide, vitamin B12, thiamin, ascorbic acid, niacin and folic acid--by high pressure liquid chromatography was examined on two bonded-phase columns, muBondapak C18 and muBondapak NH2. The effect on the retention times of individual vitamins and the separation of a multivitamin sample was determined using varying proportions of water/methanol as the eluting solvent and by addition of various salts, buffer solutions and PIC reagents to the water/methanol. Each vitamin was able to be eluted satisfactorily from muBondapak C18. It was found that seven vitamins could be resolved from a multivitamin mixture in a single analysis in several solvent systems with the total time for the analyses being always less than 40 min. With muBondapak NH2, all the vitamins except folic acid were eluted and six vitamins could be resolved from a mixture in a single analysis. The speed of analysis was greater with muBondapak NH2 with all compounds eluted in 15 min and the peaks were sharper. The order of elution was essentially the reverse of that obtained with muBondapak C18.

Chromatography, High Pressure Liquid↗
PubMed1977

Digital K-edge subtraction radiography.

K-edge subtraction images have been produced using a digital video image processor. Images formed by three filtered x-ray beams are detected by an image intensifier-Plumbicon system, digitilized, and combined in real time to produce bone- and tissue-free K-edge subtraction images of iodinated structures. Preliminary studies of rhesus monkey cranial, spinal, and abdominal structures are compared with those of conventional radiography.

Animals↗
PubMedDate not supplied

Real-time digital K-edge subtraction fluoroscopy.

We report in vitro and in vivo trials of K-edge fluoroscopy, by which iodine contrast concentration is displayed live, with tissue and bone images suppressed, free of patient-motion artifacts. Iodine and cerium, 125 and 225 mg/cm2 respectively, filter alternate TV fields of cine-pulsed 50 KVP x-rays. Weighted subtraction of successive TV fields isolates the iodine image and simultaneously minimizes artifacts. Digital techniques are used in real time. At our present x-ray tube limit, 500 mA instantaneous current, the patient exposure is 180 mR/sec and quantum mottle limits the image quality. Integrating four successive difference images provides a compromise between mottle and smoothly moving displays. Cardiovascular images of a 17-kg dog, using 1 ml/kg Renografin-60 injected into a foreleg vein, show that a 15-cm chest thickness is our present practical maximum. This method may be useful in diagnosing cardiovascular anomalies in infants without catheterization or suspension of breathing.

Animals↗